The present invention relates generally to spray dispensers that are used to apply polyurea coatings, polyurethane foam, and the like. More particularly, this invention relates to a heater system and heater control scheme for a mobile spray dispenser.
Mobile spray dispensers are used to apply a variety of materials. Spray dispensers for polyurea, polyurethane, and similar materials have separate “A-side” and “B-side” fluid systems with separate fluid reservoirs, pumps, fluid lines, and heaters. The separate “A-side” and “B-side” fluid systems carry different fluids, which are combined at a spray head to rapidly form foam or coatings. “A-side” fluids can include isocyanates, while “B-side” fluids can contain resins, polyol, flame retardants, and amine catalysts. The resulting mixture of “A-side” and “B-side” fluids typically cures in about ten seconds.
“A-side” and “B-side fluids are mixed at a sprayer disposed to aerosolize the mixed fluids and dispense the aerosol mixture on a target surface. In order to allow fluids to be sprayed, fluids in both sides are pressurized to a high pressure by separate pumps, and heated. Some spray dispensers heat fluids with dedicated heaters to reduce fluid viscosity, thereby improving fluid flow and increasing spray efficiency. Both heaters and pumps draw considerable power. In mobile systems, which may need to draw power from 120V or 230V grid power sources, it is essential that total power draw not exceed rated circuit amperage limits.